Field of the Invention
The present invention relates to vehicle technology, and more particularly, to an integrated fuel cell control system that includes a fuel processing system (FPS) and an operating method thereof.
Discussion of the Related Art
A fuel cell vehicle includes a fuel cell stack that is used as a power source, in which a plurality of fuel cells is stacked, a fuel supply system (e.g., hydrogen supply system) configured to supply a fuel, i.e., hydrogen, to the fuel cell stack, an air supply system configured to supply an oxidant necessary for electrochemical reaction, i.e., oxygen, and a thermal management system configured to adjust the temperature of the fuel cell stack.
In the fuel cell vehicle, the hydrogen supply system is configured to adjust the pressure of high-pressure hydrogen stored in a hydrogen tank using a regulator and then supply the pressure-adjusted hydrogen to the fuel cell stack, and the air supply system is configured to humidify air supplied by an air blower and then supply the humidified air to the fuel cell stack. Further, the fuel cell vehicle uses an electric motor as a driving source to drive the vehicle, and has an inverter configured to convert direct current (DC) voltage of the fuel cell stack or a battery into alternating current (AC) voltage and then drive the electric motor using the AC voltage. The fuel supply system is configured to decompress compressed hydrogen in the hydrogen tank and then supply the decompressed hydrogen to a fuel electrode (an anode) of the stack, and the air supply system is configured to supply external air, suctioned by operating the air blower, to an air electrode (a cathode) of the stack.
When hydrogen is supplied to the anode of the stack and air is supplied to the cathode of the stack, protons are separated from the anode through catalyst reaction. The separated protons are transmitted to the cathode through an electrolyte membrane, the protons separated from the anode, electrons and oxygen cause electrochemical reaction at the cathode and electrical energy may be acquired therethrough. In particular, electrochemical oxidation of hydrogen occurs at the anode, electrochemical reduction of oxygen occurs at the cathode, movement of produced electrons generates electricity and heat, and vapor or water is produced by chemical reaction, i.e., bonding between hydrogen and oxygen.
A discharge device to discharge byproducts, such as vapor, water and heat produced during the electrical energy generation process of the fuel cell stack, and non-reacting hydrogen and oxygen is provided, and gases, such as vapor, hydrogen and oxygen, are discharged to the atmosphere through an exhaust passage. Further, the fuel cell vehicle includes a substantial number of control devices. For example, the fuel cell vehicle includes controllers configured to operate and adjust respective parts, such as hydrogen, oxygen, valves, electric parts and fuel cell cooling, a high-voltage battery and power conversion controllers. Further, the fuel cell vehicle includes a fuel control unit (FCU) configured to comprehensively operate a fuel cell system.
Among controllers, a fuel processing system (FPS) is a controller in charge of on-off control of pressure sensors and valves related with hydrogen supply and may be operated based on a command from a high-level controller, i.e., an FCU. The FCU may be configured to provide a command to the FPS via controller area network (CAN) communication.
FIG. 1 is a block diagram illustrating a conventional fuel cell control system according to the related art. An FCU 90 is connected directly to one hydrogen valve 10 and is configured to operate the hydrogen valve 10; an FPS 80 is connected directly to a hydrogen drain valve 20 and a hydrogen purge valve 30 and is configured to operate the hydrogen drain valve 20 and the hydrogen purge valve 30. The FCU 90 is configured to receive values, sensed by a pressure sensor 40, a water level sensor 50 and a hydrogen sensor 60, from the FPS 80 and transmit cooperative control a command regarding hydrogen supply to the FPS 80.
As described above, in the conventional fuel cell control system, the FCU and the FPS are separated from each other. Direct control by the FPS is advantageous in that an air blower may be directly driven and fault diagnosis may be directly executed. However, since the FCU and the FPS are separated from each other, the conventional fuel cell control system has many drawbacks, such as generation of noise between controllers, increase in costs, difficulty in formation of a package, complex cooperative control, reduction in control efficiency, increase in weight, increase in wire complexity, etc. Therefore, an improved fuel cell control system is required.